to be effective, show results ☊ 
có hiệu lực có hiệu quả 
efficient like: có hiệu quả → →
wirksam ☊ 
có hiệu quả ☊ 
有效的 ☊ yǒuxiào de wirksam ☊ có hiệu quả ☊ ☊ We can try that—but whether it'll work is another matter. ☊ another ☊
it is demonstrated that...: It has been demonstrated that this drug is effective. ☊ demonstrate ☊
drugs that are effective against cancer ☊ effective ☊
The company must reduce costs to compete effectively. ☊ effectively ☊
For maximum effect do the exercises every day. ☊ maximum ☊
The experiment had the reverse effect to what was intended. ☊ reverse ☊
In order that training should be effective it must be planned systematically. ☊ should ☊